The invention relates to a water-repellent composition, referred to as an anti-wetting composition, a rain-repellent composition, which makes it possible to prevent the deposition of liquid, in particular of water or an aqueous liquid, on a surface; it relates in particular to a composition for preventing the deposition of water or for driving off rainwater or any other water sprayed onto a preferably transparent surface, in particular a glass surface, for example the surface of a window and in particular the surface of a windshield of a motor vehicle or alternatively of an aircraft.
Several solutions have been provided for removing or repelling liquids and in particular rain or other fluids sprayed onto windows and other transparent surfaces, such as the windshields of motor vehicles or boats, in order in particular to maintain clear vision through these windshields, which clear vision is essential in ensuring the comfort and the safety of travellers. Indeed, the problem of visibility in heavy rain is one of the oldest problems encountered, in particular in the automobile section.
The solutions envisaged can be put into two main categories:
mechanical means,
chemical means.
In the first category, windshield wipers have been and are employed with success on windshields, but also on other glass surfaces, such as headlamp lenses or automobile, boat or locomotive windows.
However, to be efficient, windshield wipers require high sweeping rates and consequently result in a high consumption of electricity in employing the associated devices. They also tire out the driver of said vehicle.
The second category of solutions envisaged is that of chemical means, it being possible for these means to be used alone or in addition to the mechanical means described above. These means generally consist in rendering the surface hydrophobic, that is to say non-wettable by water. In other words, on the treated surface, for example the external surface of the windshield rendered non-wettable because of the hydrophobic coating which it carries, the water is instantly converted into minuscule droplets which are entrained by the high-speed airstream which sweeps the windshield. Excellent visibility can thus be obtained, a visibility superior to that of the mechanical processes employed alone.
Numerous documents exist relating to the application of coatings to surfaces, in particular transparent surfaces, in order to render them water-repellent or non-wettable.
U.S. Pat. No. 2,612,458 and U.S. Pat. No. 2,777,772 disclose water-repellent products composed of substitution polysilanes applied by rubbing with a frictional agent on a clean and dry-windshield.
U.S. Pat. No. 2,923,633 relates to water-repellent or rain-repellent products for windshields, in particular for the windshields of vehicles which are moving at high speed, which comprise polysilanes comprising alkoxy groups. These products are mixed with carbon black or rouge, which acts as frictional agent, in order to form a paste which is applied by rubbing on the clean and dry windshield. The application of an additional wax layer is not necessary.
U.S. Pat. No. 2,962,390 relates to a water-repellent composition in which first of all a paste of alkylalkoxysilane with, for example, carbon black is applied to a surface to be treated, which paste is hydrolyzed and then covered with a layer of water-repellent paraffin wax and a polyamide resin. The treated surface must be clean and dry.
These compositions exhibit the significant disadvantage of requiring application operations which are often lengthy and complicated. Numerous water-repellent compositions also require a curing stage, in particular a heat-curing stage, in order to be able to be operational; for this reason, their use, despite the excellent protection obtained, is extremely restricting.
For this reason, other water-repellent compositions comprise alkylpolysiloxanes and strong acids in a solvent and are disclosed in particular in U.S. Pat. No. 3,579,540; these compositions form a long-lasting highly resistant film but also exhibit the essential disadvantage of being corrosive, in particular for metal components.
Patent Application JP 07 041 336 discloses a rain-repellent composition for automobile windows which comprises a modified aminopolysiloxane, an alcohol, water and formic acid.
U.S. Pat. No. 5,021,089 discloses noncorrosive water-repellent compositions which are devoid of strong acid and which comprise a silyl phosphate, an organopolysiloxane (dimethylpolysiloxane) and a volatile organic solvent which can be an organopolysiloxane (oligomer). These compositions are applied to clean and dry glass surfaces in order to form a uniform film and cannot be applied when it is raining.
Likewise, Patent Application FR-A-2 662 171 relates to a noncorrosive water-repellent composition for nonporous materials comprising an alkylpolysiloxane, for example a dimethylpolysiloxane, and sodium silicate. In order to apply, it is necessary first to clean and dry the surface to be treated, to allow the coating to dry and to polish.
All the compositions mentioned above are compositions which have to be applied according to a restricting procedure. In addition, the coating applied only has a limited lifetime and disappears as a result of erosion by rain, hail, snow, ice crystals, dust and sand.
The active products applied have to satisfy a large number of requirements, listed for example in U.S. Pat. No. 3,433,750, such as in particular:
they must exhibit a favorable refractive index,
they must be nonaggressive with respect to the materials of the surfaces to which they are applied, in particular with respect to the organic and metallic materials employed in automobiles,
they must be nontoxic.
The products of the prior art which are currently the most commonly used, while they are satisfactory as regards the majority of the preceding requirements, exhibit, however, the disadvantage of leaving deposits on the surfaces, such as the windows, during drying which are difficult to remove. These deposits are a relatively minor nuisance with respect to the visibility but aesthetically harmful with respect to the external appearance of the automobile. These disadvantages are intensified by the successive spraying and deposition of several layers of products, thus resulting in an increasing lack of visibility. In addition, these sprayable compositions comprise, as carrier solvent or fluid, compounds of CFC or chlorofluorocarbon type belonging to the family of the Freons(copyright), F 113 (1,1,2-trichloro-1,2,2-trifluoroethane), which are responsible for the destruction of the stratospheric ozone layer and the use of which is subject to increasingly strict regulations which have resulted, according to the Montreal Protocol, in a complete ban on them from January 1, 1996.
The replacement of compounds of CFC type by compounds of HCFC type, such as F141b, has been envisaged but increasingly strict regulations targeted at banning in the more or less long term the use of such compounds have been or will be promulgated in many countries.
It is thus imperative to employ other carrier solvents or fluids which do not exhibit such a negative influence on the ozone layer. However, the search for such compounds, when they have to be employed as specific solvents for water-repellent products, encounters a great many difficulties as these solvent compounds have to satisfy a great many criteria which are difficult to harmonize from the viewpoint in particular of their toxicity (an important factor, in particular in the case of a leak), stability, density or vapor pressure and of their compatibility with the water-repellent active products and with the propellant gas and optionally with the other compounds which can be included in the composition and optionally the materials encountered during its application.
A subject matter of the invention is thus a water-repellent, also known as rain-repellent, composition which is not polymerized on contact with the air, does not leave hardened deposits and marks on the treated surfaces and has excellent water-repellent effectiveness in heavy rain and which also fulfils all the conditions mentioned above for such compositions and in particular complete solubilization and stability of the active compound over a wide temperature range, for example from xe2x88x9255xc2x0 C. up to 80xc2x0 C.
Another object of the invention is to provide a water-repellent composition which can be sprayed in the form of an aerosol and which can comprise a carrier fluid or a solvent which fulfils, inter alia, the abovementioned conditions, in conformity with the regulations banning compounds which are harmful to the ozone layer, and which is compatible with the active product, that is to say which in particular dissolves the latter over the entire temperature range, and the repellent gas, this composition being packaged in a container pressurized with an inert gas.
These objectives and also others are achieved according to the present invention by a water-repellent composition, also known as a rain-repellent composition, composed of at least one hydrophobic active agent and of at least one solvent which is compatible with the hydrophobic active agent, this solvent being other than a fluorinated hydrocarbon, characterized in that the solvent is an organic compound comprising at least one oxygen-comprising functional group and in that the hydrophobic active agent is a compound of organopolysiloxane type.